1. Technical Field
The present invention relates to a robot, a robot system, and a robot control device.
2. Related Art
A robot including a robot arm has been known. A plurality of arm members are coupled via joint sections in the robot arm. For example, a hand is attached to the arm member on the most distal end side as an end effector. The joint sections are driven by motors. The arm members turn according to the driving of the joint sections. The robot performs work for, for example, gripping a target with the hand, moving the target to a predetermined place, and inserting the target into an opening.
A force sensor is provided between the arm member on the most distal end side and the hand. In performing the work, the robot detects a force and a moment with the force sensor and performs impedance control (force control) on the basis of a detection result of the force sensor.
In the force sensor, accuracy of force detection is deteriorated because of a temperature change, an output drift due to a leak current of a circuit, and the like. Therefore, in performing the work, the robot performs zero-point correction (initialization) of the force sensor (see, for example, JP-A-2009-23047 (Patent Literature 1)). According to the zero-point correction of the force sensor, it is possible to improve the accuracy of the force detection.
JP-A-2005-81477 (Patent Literature 2) discloses, as a robot system, an automatic polishing apparatus that performs polishing by moving a polishing tool (a Leutor). The automatic polishing apparatus performs operation for measuring, with a polishing force measuring device (a force sensor), a polishing force applied to the polishing tool, moving the polishing tool on the basis of the measured polishing force, and keeping the polishing force fixed (see paragraph “0014” and FIG. 4 of Patent Literature 2).
However, in the robot in the past, as shown in FIG. 17, as work performed using the force sensor, when the robot arm is moved from a first position to a second position, the target is inserted into the opening, and thereafter the robot arm is moved to a third position, the zero-point correction of the force sensor needs to be performed in a state in which the robot arm is stopped in the first position. Consequently, a cycle time increases in the work performed using the force sensor.
In the robot system described in Patent Literature 2, since the force sensor is present on the Leutor side where a rotating shaft rotates at high speed, a vibration component (noise) caused by the high-speed rotation of the Leutor is superimposed on the polishing force detected by the force sensor. In the case of the rotating polishing tool such as the Leutor, reaction due to a gyro effect, which occurs when an object having an inertial moment is moved, also occurs. Therefore, the polishing tool is moved on the basis of an output value of the force sensor affected by the noise and the reaction is moved. Therefore, the control for keeping the polishing force (the force applied to the target) fixed cannot be accurately performed.